Temperature-controlled thermal platform for automated testing

ABSTRACT

A temperature-controlled system and method for supporting a wafer or packaged integrated circuit (IC) under test are described. The system includes a thermal platform having a top surface assembly on which the wafer or IC can be mounted. A thermal plate is located under and in thermal communication with the top surface assembly. The thermal plate is made of a porous thermally conductive material. A temperature-controlled fluid such as air enters and propagates radially through the porous material of the thermal plate. The temperature of the wafer or IC is controlled by controlling the temperature of the air passing through the thermal plate. The plate can be made of a sintered metal such as copper or a reticulated foam or a carbon or graphite foam.

RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/908,149, filed on Jul. 18, 2001, which is based on U.S.Provisional Patent Application No. 60/220,016 filed on Jul. 21, 2000 andNo. 60/267,830 filed on Feb. 9, 2001. The contents of all of the priorapplications are incorporated herein in their entirety by reference.

BACKGROUND OF THE INVENTION

[0002] In fabrication of integrated circuits (ICs), it is important totest the individual circuit chip die while they are still attached in asemiconductor wafer and to test the packaged integrated circuit devices.In many testing applications, the tests must be performed overtemperature. Accordingly, automated test systems are commonly outfittedwith temperature control systems which can control the temperature ofthe wafer or device under test.

[0003] In some testing systems, such as wafer probers, the wafer is heldon a temperature-controlled chuck, and electrical stimulus signals areapplied to the circuits on the wafer, circuit response signals aredetected via an array of electrical contact probes brought into contactwith the wafer. The temperature of the chuck and, therefore, thetemperature of the wafer, can be controlled by a heater and/or heat sinkintegrated into the chuck and by temperature-controlled fluid circulatedthrough the chuck. Such systems are manufactured and sold by Temptroniccorporation of Sharon, Mass.

[0004] In other systems, packaged ICs are tested over temperature byapplying the electrical stimulus signals and receiving response signalsvia the IC package pins. The device under test (DUT) is held in a socketon a platform, and the test signals are routed to the pins via thesocket. In one such system, the THERMOSTREAM™ system manufactured andsold by Temptronic Corporation, a temperature-controlled steam of air isdirected onto the DUT to control the temperature of the DUT duringtesting.

[0005] As wafers become larger, and as circuits become smaller and moredensely integrated, positioning tolerances for these test systems becomesmaller. Accordingly, it is becoming increasingly important that thesupport system on which the DUT or wafer is supported be mechanicallystable and rigid and also extremely flat, since mechanical flaws such asdistortions in the platform would adversely affect the positioningcapability of the system. This is particularly important intemperature-controlled test systems, since mechanical systems tend todistort and warp over temperature. Particularly at high temperature,distortions in the support platform can become so great that substantialinaccuracies in testing can result.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a mechanically stabletemperature-controlled platform for supporting a workpiece such as awafer or a packaged IC DUT during testing which eliminates thesedrawbacks. In accordance with the invention, there is provided a thermalplatform and method for supporting a workpiece. The platform includes atop surface assembly on which the workpiece can be mounted. A thermalplate made of a porous thermally conductive material is located inthermal communication with the top surface assembly. A fluid inletallows a temperature-controlled fluid, for example, air, to enter thethermal plate and propagate through the porous material of the thermalplate. A temperature controller controls the temperature of the fluid tocontrol the temperature of the workpiece.

[0007] In one embodiment, the workpiece is a semiconductor wafer onwhich are formed one or more integrated circuits. In another embodiment,the workpiece is a packaged integrated circuit.

[0008] In one embodiment, the thermal platform is contained within atest system for testing the workpiece. For example, the test system canbe a wafer prober machine or a packaged IC device handler. At least aportion of the temperature controller can be externally located suchthat it is connected to the test system via a hose. The temperaturecontroller includes a fluid source for providing thetemperature-controlled fluid to the test system via the hose. The oneparticular embodiment, the temperature controller includes a fluidheater located in the test system for heating the fluid.

[0009] In one embodiment, the porous thermally conducted materialcomprises a sintered metal. In another embodiment, the materialcomprises reticulated foam. The thermally conducted material can includecopper. It can also comprise a carbon and/or graphite foam.

[0010] The thermal platform can include a layer of channels adjacent tothe thermal plate which facilitate the flow of fluid through the thermalplate. The channels can be arranged in a radial spiral pattern tofacilitate the flow of fluid radially from a central portion of thethermal plate to its perimeter. The channels can be formed in one ormore surfaces of the thermal plate. Alternatively, the channels can beformed in a separate convector plate located adjacent to the thermalplate.

[0011] In another aspect, the invention is directed to an apparatus andmethod for testing an integrated circuit. The apparatus includes a testcircuit in which the integrated circuit is supported. A temperaturecontrol is coupled to the test system. The temperature control systemincludes a fluid source for providing a fluid to the test system inthermal communication with the integrated circuit. A controller in thetemperature control controls the temperature of the fluid to control thetemperature of the integrated circuit. A fluid heater for heating thefluid is located within the test system.

[0012] In one embodiment of this aspect of the invention, the testsystem is a wafer prober. In another embodiment, the test system is apackaged integrated circuit device handler. Accordingly, the IC can bepart of an IC wafer or it can be packaged in an IC package.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

[0014]FIG. 1 is a schematic functional block diagram illustrating anautomated test system in accordance with the present invention.

[0015]FIG. 2 contains a schematic cross-sectional view of one embodimentof the thermal platform of the invention.

[0016]FIG. 3 contains a schematic pictorial view of the radial flow ofthe temperature-controlled fluid through the porous thermal plate of theinvention.

[0017]FIG. 4 is a schematic plan view of one embodiment of the thermalplate of the invention in which a spiral pattern of channels or groovesis formed to aid in distributing temperature-controlled fluid from acentral aperture to the circumferential edge of the thermal plate, inaccordance with the invention.

[0018]FIGS. 5A through 5C illustrate various embodiments of the thermalplate and top surface assemblies of the invention including one or moreadditional layers.

[0019]FIG. 6 is a schematic plan view of a surface of a convector platein accordance with one embodiment of the invention.

[0020]FIG. 7 is a schematic block diagram of one embodiment of anin-line fluid heater in accordance with the invention.

[0021]FIG. 8 is a schematic cross-sectional diagram of a thermalplatform in which the temperature-controlled fluid circulated throughthe porous thermal plate is recovered, in accordance with the invention.

[0022]FIG. 9 contains a schematic cross-sectional diagram of anotherembodiment of the thermal platform of the invention in which thetemperature-controlled fluid is circulated radially from the perimeterto the center of the thermal plate and from the center back out to theperimeter.

[0023]FIG. 10 contains a schematic cross-sectional diagram of anotherembodiment of the thermal platform of the invention in which a heater isattached below the porous thermal plate.

[0024]FIG. 11 contains a schematic cross-sectional diagram oneembodiment of the heater included in the thermal platform of FIG. 10.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0025]FIG. 1 is a schematic functional block diagram illustrating anautomated test system 10 in accordance with the present invention. Asshown in FIG. 1, the system 10 includes a temperature controller 12which can be of the type manufactured and sold by Temptronic Corporationof Sharon, Mass. under the name THERMOSTREAM™. The temperaturecontroller 12 includes an air source 16 which provides cold air along agas hose 18 to the test system 14. The hose 18 can be acondensation-free hose of the type described in U.S. Pat. No. 6,070,413,issued on Jun. 6, 2000, assigned to Temptronic Corporation andincorporated herein by reference. The test system 14 can be a waferprober or packaged device handler system for testing a workpiece 24, forexample, wafers or packaged ICs, over temperature. A test controller 30controls the application of stimulus signals to and detection andprocessing of response signals from the workpiece 24 via attester unit28.

[0026] The temperature of the platform 26 and the workpiece 24 arecontrolled by the temperature controller 12. The temperature of thestream of air from the air source 16 is controlled to control thetemperature of the workpiece 24. The stream of air enters the testsystem 14 at a heater 20, which heats the cool air as required to setthe temperature of the workpiece 24 at the desired test temperature.Temperature sensors are provided both at the platform 26 and theworkpiece 24. A temperature sensor can be provided as atemperature-sensitive circuit element integrally fabricated into theworkpiece 24, in accordance with U.S. patent application Ser. No.09/612,667, filed on Jul. 10, 2000, now U.S. Pat. No. 6,545,494, andU.S. patent application Ser. No. 09/839,274, filed on Apr. 20, 2001, nowU.S. Pat. No. 6,552,561, both of which are assigned to TemptronicCorporation and are incorporated herein by reference.

[0027] The temperature controller 12 can use an auto-cascaderefrigeration unit to provide the stream of cool air. This is a singlecompressor multiple refrigerant system which operates best underconstant load. The unit is capable of producing supply air or gastemperatures as low as −85 degrees C. In another embodiment, the sourcecould use a cascade refrigeration system, such as a two-stage cascaderefrigeration system to achieve ultimate temperature lows. A unit withliquids being used as the control medium could also be used.

[0028] The temperature control approach can be implemented as adual-loop temperature control of the type described in U.S. Pat. No.4,734,872, issued on Mar. 29, 1988, assigned to Temptronic Corporationand incorporated herein by reference. Using the dual-loop control, thetemperature of the workpiece and the air stream are monitored. Thetemperature of the workpiece is controlled by altering the temperatureof the air stream to maintain the temperature of the workpiece at thedesired temperature set point. To that end, temperature feedback signalsindicating the temperature of both the workpiece 24 and the air streamare provided to the temperature control processor 22 via lines 32. Whereit is desired to alter the temperature of the air stream, the heater 20can be selectively activated to raise the temperature or deactivated tolower the temperature.

[0029] In accordance with the invention, the platform 26 is configuredto provide accurate, precise and uniform temperature control with veryfast temperature transitions. FIG. 2 contains a schematiccross-sectional view of one embodiment of the thermal platform 26 of theinvention. The platform 26 includes a top surface 126 on which thetemperature-controlled workpiece 24 (not shown) can be supported duringtesting. The top surface 126 can be configured according to the testingapplication. For example, the top surface 126 can serve as a platen forelectronic package test, a thermal platform for a wafer test, or athermal platform for coating compact disks with ferrous coating.

[0030] The top surface assembly 126 is mounted over and in thermalcommunication with a thermal plate layer 128. The thermal plate 128 canbe mechanically attached to the top surface assembly 126, such as byscrews, pins, brazing, welding, etc. The thermal plate can also beadhered to the top surface assembly such as by a thermally conductiveadhesive. The temperature of the thermal plate 128 is controlled tocontrol the temperature of the top surface assembly 126 and theworkpiece mounted thereon. In accordance with the invention, temperatureis controlled by distributing temperature-controlled fluid, e.g., air,radially through the thermal plate 128. The thermal plate 128 is made ofa porous thermally conductive material such as copper or carbon. Thetemperature-controlled fluid enters the thermal plate 128 through aninlet 132 and is conveyed to a central plenum 130. The fluid flows intothe plate 128 at a centrally located aperture 134 in the plate 128. Thefluid flows radially through the porous material of the plate 128 andexits the plate at the circumferential edge 136 of the plate 128. Thefluid then exits the platform 26 via an outlet 138. FIG. 3 contains aschematic pictorial view of the radial flow of thetemperature-controlled fluid through the porous thermal plate 128.Referring again to FIG. 2, the fluid is contained within the porousthermal plate 128 at its bottom surface by a layer of material 129. Thematerial 129 can be a flame sprayed ceramic barrier layer or ahigh-temperature varnish. The material layer 129 prevents the fluid fromescaping from the porous thermal plate 128 through its bottom surface.

[0031] The porous thermal plate 128 transfers the thermal energy fromthe circulating medium, e.g., air, to the top surface assembly 126 and,therefore, the workpiece, in a highly efficient manner. The thermalplate 128 is made of a porous thermally conductive material such ascopper. The material can be sintered metal or reticulated foam.Alternatively, the material can be a high thermal conductivity carbon orgraphite foam, such as that being developed by the Oak Ridge NationalLaboratory. The porosity of the material reduces its mass and alsoprovides greatly increased surface area. Because of the reduced mass,much lower energy is required to transition temperature than would berequired in a solid material of the same size. Also, the increasedsurface area of the porous material provides highly efficient heattransfer through the material. Also, the porous nature of the materialcreates a turbulent flow of the fluid through the medium, therebyblending the heating and cooling fluid medium and enhancing theuniformity of the temperature within the medium and on the workpiece.The uniformity of the porosity of the material of the thermal plate 128allows for uniform fluid flow throughout the thermal medium, therebyestablishing a uniform temperature distribution. Since the porousthermal medium is in thermal communication with the top surface assembly126, it provides a highly uniform top surface temperature for thethermal platform. Also, the resulting reduction in thermal gradients onthe surface enhances the flatness of the surface by reducing thermalexpansion and contraction effects. Because of the mechanical heattransfer properties related to the thermal medium, the medium is alsohighly effective in heat sinking and absorbing thermal energy generatedby power generating devices while they are under electrical test.

[0032] The surface of the thermal platform 26 and the porous thermalmedium 128 can be made of common materials such as copper that have goodthermal conductivity. Also, they have closely matched coefficients ofexpansion. With the distributed temperature uniformity and materialsimilarities, there is little mechanical stress due to thermal growth todistort the surface and reduce its flatness. Because of the high degreeof flatness, good contact is maintained between the wafer or deviceunder test and the test equipment.

[0033] In one embodiment, even distribution of thetemperature-controlled fluid is aided by a pattern of distributiongrooves or channels formed in the thermal plate 128. FIG. 4 is aschematic plan view of one embodiment of the thermal plate 128 in whicha spiral pattern of grooves 131 is formed to aid in distributing thefluid from the central aperture 134 to the circumferential edge 136 ofthe thermal plate 128. The grooves 131 can be etched, formed, machinedor cast into the top and/or bottom surfaces of the thermal plate 128.The grooves 131 are shown in FIG. 4 as being distributed over only aportion of the surface of the thermal plate 128. However, it will beunderstood that any portion of the surface can include the distributiongrooves. In one particular embodiment, the grooves 131 are distributedover the entire surface of the plate 128 in the spiral patternillustrated in the figure.

[0034] In another embodiment, the thermal plate 128 has additionallayers attached to its top and/or its bottom surface. FIGS. 5A through5C illustrate various embodiments of the thermal plate and top surfaceassemblies of the invention including one or more additional layers. InFIG. 5A, the porous thermal plate 128 is attached or adhered to thebottom of the top surface assembly 126. A bottom layer 201 of ceramic orhigh temperature varnish is attached to the bottom of the plate 128. InFIG. 5B, a layer of material 203 that is impervious to air is bonded tothe lower surface of the thermal plate 128. In FIG. 5C, a three-layersandwich structure is formed with layers 205, 207 of highly thermallyconductive material bonded or attached to the top and bottom surfaces ofthe thermal plate 128. As in the other embodiments, the sandwichstructure is bonded, adhered or fastened to the bottom of the topsurface assembly 126 to be in intimate thermal contact with the assembly126.

[0035] The thermal plate 128 transfers the thermal energy from the fluidthrough the porous material to the top surface assembly 126 to which itis attached in a highly efficient manner. The surface assembly 126 ofthe platform 26 will in turn transfer the thermal energy into or out ofa wafer or electronic package directly or indirectly through one or morelayers of thermally conductive material. In one embodiment, one suchlayer is a convector plate disposed between the thermal plate 128 andthe top surface assembly 126 or at the bottom of the thermal plate 128.FIG. 6 is a schematic plan view of a surface of a convector plate 301 inaccordance with one embodiment of the invention. The convector plate 301can be bonded or mechanically attached to the thermal plate 128 and isalso used to seal the surface of the plate 128 to prevent thetemperature-controlled fluid from escaping through the surface of theporous thermal plate 128. As shown in FIG. 6, each surface of theconvector plate 301 can be formed with a pattern of channels used tofacilitate the flow of fluid across the surface of the plate 301. In theparticular plate 301 shown in FIG. 6, a pattern of spiral radial groovesis formed to assist in conducting the fluid from the central aperture tothe perimeter of the device. Other patterns can also be used. Forexample, patterns of circular void regions can be formed in thesurface(s) of the plate 301. The convector plate can be made of a highlythermally conductive material. The pattern of channels or grooves can bemachined or photo etched into the surface of one or both sides of theplate 301.

[0036] In addition to, or instead of, the convector plate 301, otheradditional layers can also be disposed in proximity to the porousthermal plate 128. These additional layers can be maintained in contactwith the thermal platform, mechanically or by vacuum. The additionallayers can include features such as vacuum hold down patterns for wafersand/or electrical isolation layers such as polyamide and ceramics.

[0037]FIG. 7 is a schematic block diagram of one embodiment of anin-line heater 20 in accordance with the invention. As described inconnection with FIG. 1, the heater 20 is used to heat the air from theair source 16 in the temperature controller 12. The hose 18 is connectedto the heater 20 by a quick disconnect clamp 302. Cool air enters theheater 20 from the hose 18 and passes into a turbulence generator 304which creates a turbulent flow in the air stream. The turbulent flowprovides more uniform temperature distribution. Next, the air passes tothe heater 316 which heats the air. Next, the heated air enters a mixingchamber 310, and the turbulent heated air exits the heater 20 and isconveyed to the inlet of the thermal platform 26 (FIG. 1).

[0038] The heater 20 is insulated from the system environment byinsulation 314. An air temperature sensor arrangement 312 can be locatednear the heater outlet. Also, a platform temperature sensor 308 can belocated on the heater 20. Alternatively, the platform temperature sensorcan be located on the platform. The sensors 308 and 312 provide theirrespective temperature sense signals on sense lines 306.

[0039] The location of the heater 20, i.e., within the prober orhandler, allows for maximum heat transfer to the thermal platform 26 andminimizes transition time. The greater the distance from the temperaturesource, the greater the mass that must be transitioned. By placing theheater in the prober or handler, there is less mass that must betransitioned, leading to lower transition times. That is, only the linesfrom the heater section 20 are required to transition from cold to hot.This technique minimizes the amount of mass to transition and maximizesthe speed of transition. The heater section 20 is designed to mix theair and to maximize heater efficiency. It is also designed for ease ofattachment to the cold air source and to provide air at a uniformtemperature to the thermal platform.

[0040] In one embodiment, the temperature-controlled fluid is capturedas it escapes the porous perimeter of the thermal plate 128. FIG. 8 is aschematic cross-sectional diagram of a thermal platform 226 in which thetemperature-controlled fluid circulated through the porous thermal plate128 is recovered, in accordance with the invention. The thermal platform226 of FIG. 8 includes a housing 149 which contains the fluid, i.e.,air, as it exits the porous thermal plate 128 at its perimeter edge 145.The air passes into a chamber 141 and exits the chamber through anexhaust port 143 where it can be recycled or discarded. This recaptureof the air prevents the overheating or overcooling of the test system,i.e., prober or handler, in which the platform 226 is used. Also, therecovery plenum avoids the impact of the air flow on the needles usedfor probing wafers, thereby reducing bounce of jitter of the needles.This results in more stable test results.

[0041] The embodiment of FIG. 8 also illustrates an approach toattaching the top surface assembly 126 to the thermal plate 128 whichreduces distortion in the platform 226. Retaining clips 147, made of aspring metal, are used to hold the top surface 126 and the thermal plate128 together. By attaching the two without the rigid constraint of suchapproaches as screws, rivets, etc., the two layers are allowed to expandand contract laterally relative to each other. This eliminatessubstantial distortion and warp effects due to the difference in thermalexpansion coefficient of the two layers.

[0042]FIG. 9 contains a schematic cross-sectional diagram of anotherembodiment of the thermal platform 326 of the invention in which thetemperature-controlled fluid is circulated radially from the perimeterto the center of the thermal plate and from the center back out to theperimeter. According to this embodiment, the air enters the platform 326at an inlet 405 and passes through a chamber 409 enclosed by the housing407. The air passes up through an opening 413 and is conveyed along thebottom surface 503 of a convector plate 501, described above inconnection with FIG. 6. In this embodiment, the convector plate 501 haschannels formed on both its top and bottom surfaces to assist in theflow of the fluid from the perimeter to the center along the bottomsurface 503 and then from the center back out to the perimeter along thetop surface 505. When the air reaches the cental aperture 411, it entersthe region above the plate 501 and flows along the top surface 505radially back out to the perimeter of the plate 501, using the channelsformed in the surface to assist in the flow. The air then passes out ofthe platform 326 through an outlet 406 where it can be recovered ordiscarded.

[0043] In automated testing, there are applications in which electricalisolation is extremely important. There are also applications in whichelectromagnetic fields and intense X-rays could disrupt the test processor cause standard heating elements to deteriorate. The foregoingdescribes an approach to achieving heating and cooling of a platformusing a fluid media such as air, gas or liquids without the need forheating elements within the platform. However, in one embodiment, anoptional heater can be used within the platform.

[0044] In the embodiments described thus far, a heater can be added tothe platform above or below the thermal plate 128. FIG. 10 contains aschematic cross-sectional diagram of another embodiment of the thermalplatform 526 of the invention in which a heater 529 is attached belowthe porous thermal plate 528. In one embodiment, the heater 529 is aMica or foil type heater. The heater 529 is used to provide additionalheating of the platform 526 where required. The heater 529 is added tobuffer the final temperature or in cases where the temperature set pointof the air is in excess of the ability of the air supply line to carrythe pressure to operate the system at temperature.

[0045] The heater 529 is of a multi-layered configuration. FIG. 11contains a schematic cross-sectional diagram of one embodiment of theheater 529 included in the thermal platform 526 of FIG. 10. Themulti-layered construction provides high electrical and noise isolation.Within the heater 529, the conductive heater element 533 is surroundedby layers 535 and 537 of Mica or Kapton insulation material. Theselayers are covered with a metal shield layer 539 and 541. These layersare then covered with Mica or Kapton layers 543 and 545.

[0046] The metal shield layers 539 and 541 are tied to ground tominimize radiated noise from the heater foil or element. The heater 529is adhered, attached or fastened to the thermal plate 528.Alternatively, it can be held in place by compression from the thermalplate 528. The heater 529 provides the ability to boost the temperatureof the thermal plate 528. The heater 529 can have elements or foil whichallow for tuning of the thermal gradient.

[0047] While this invention has been particularly shown and describedwith references to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the following claims.

1. A temperature-controlled system for supporting a workpiececomprising: a top surface assembly on which the workpiece can bemounted; a thermal plate in thermal communication with the top surfaceassembly, the thermal plate being formed of a porous thermallyconductive material; a fluid inlet for allowing a temperature-controlledfluid to enter the thermal plate and propagate through the porousmaterial of the thermal plate; a layer of channels at a surface of thethermal plate for facilitating the flow of the fluid through the thermalplate; and a temperature controller for controlling temperature of thefluid propagating through the thermal plate to control the temperatureof the workpiece.
 2. The system of claim 1, wherein the workpiece is asemiconductor wafer.
 3. The system of claim 1, wherein the workpiece isa packaged integrated circuit.
 4. The system of claim 1, wherein thefluid is air.
 5. The system of claim 1, wherein the thermal platform iscontained within a test system for testing the workpiece.
 6. The systemof claim 5, wherein at least a portion of the temperature controller isexternally connected to the test system, the temperature controllercomprising a fluid source for providing the fluid to the test system. 7.The system of claim 6, wherein the temperature controller comprises aheater inside the test system for heating the fluid.
 8. The system ofclaim 1, wherein the test system is a wafer prober.
 9. The system ofclaim 1, wherein the test system is a packaged device handler.
 10. Thesystem of claim 1, wherein the porous thermally conductive materialcomprises sintered metal.
 11. The system of claim 1, wherein the porousthermally conductive material comprises reticulated foam.
 12. The systemof claim 1, wherein the porous thermally conductive material comprisescopper.
 13. The system of claim 1, wherein the porous thermallyconductive material comprises carbon foam.
 14. The system of claim 1,wherein the porous thermally conductive material comprises graphitefoam.
 15. The system of claim 1, wherein the channels are formed in asurface of the thermal plate.
 16. The system of claim 1, wherein thechannels are formed in a convector plate adjacent to the thermal plate.17. An apparatus for testing an integrated circuit comprising: a testsystem in which the integrated circuit is supported; a temperaturecontrol coupled to the test system, the temperature control comprising:a fluid source for providing a fluid to the test system in thermalcommunication with the integrated circuit; a controller for controllingthe temperature of the fluid to control the temperature of theintegrated circuit; and a fluid heater for heating the fluid, the fluidheater being located within the test system.
 18. The apparatus of claim17, wherein the fluid is air.
 19. The apparatus of claim 17, wherein thetest system is a wafer prober.
 20. The apparatus of claim 17, whereinthe test system is a packaged integrated circuit device handler.
 21. Theapparatus of claim 17, wherein the integrated circuit is part of anintegrated circuit wafer.
 22. The apparatus of claim 17, wherein theintegrated circuit is packaged.